Normally when hydrocarbon fuels are burned in internal combustion engines, exhaust gases are produced containing significant quantities of pollutants like carbon monoxide, oxides of nitrogen and unburned hydrocarbons. Typically, after-treatment devices like oxidizing catalysts are used to reduce the pollutant content of the exhaust. However, an engine producing significant amounts of unburned hydrocarbons will have a low energy efficiency.
Attempts have been made in the past to cause more complete combustion of hydrocarbon fuels in internal combustion engines. For example, U.S. Pat. No. 4,198,940 issued to Ishida; U.S. Pat. No. 2,113,602 issued Pratt; U.S. Pat. No. 4,059,076 issued to Kosaka and U.S. Pat. Nos. 3,958,540; 3,896,774; and 3,924,576 issued to Siewert all disclose internal combustion engines, in which exhaust from one cylinder of the engine is delivered to and burned in a second cylinder to reduce the emission of unburned hydrocarbons.
When hydrogen is burned in an internal combustion engine, the exhaust generally comprises only water vapor and the oxides of nitrogen. It has been found that the emissions of the oxides of nitrogen can be reduced if the oxygen content of the charge is reduced to an amount below that normally present in the air. Thus, engines using hydrogen can be operated to produce exhaust gases having a very low pollutant content. However, hydrogen is expensive to produce and occupies approximately four times the volume of hydrocarbon fuel of the same energy potential.
An object of this invention is to provide an improved fuel supply system and combustion process for an internal combustion engine burning hydrocarbon fuel that significantly reduces exhaust emissions of carbon monoxide, oxides of nitrogen and unburned hydrocarbons without the need for after-treatment devices.
Another object of this invention is to provide an improved fuel supply system and combustion process for an internal combustion engine, enabling the engine to use hydrogen and hydrocarbon fuels to produce exhaust gases having a low pollutant content similar to exhaust gases produced by an engine burning only hydrogen.